1. Field of the Invention
The present invention relates to a method of manufacturing a seal part in which gaskets made of a rubber material or a synthetic resin material having a rubber-like elasticity are integrally formed on a film, a sheet or a plate-shaped base frame, for example, a fuel battery seal for sealing a flow path formed in each of fuel battery cells of a fuel battery stack.
2. Description of the Conventional Art
A fuel battery has a stack structure in which a fuel battery cell is formed by holding a power generation body including a membrane electrode assembly (MEA, a membrane-electrode complex), in which a pair of electrode layers are provided on both surfaces of an electrolytic membrane, by and between separators, and a lot of the fuel battery cells are laminated. Further, air (oxygen) is fed to one catalyst electrode layer (an air pole) from an air flow path formed in one surface of each of the separators, fuel gas (hydrogen) is fed to the other catalyst electrode layer (a fuel pole) from a fuel gas flow path formed in the other surface of each of the separators, and electric power is generated in accordance with an electrochemical reaction corresponding to a reverse reaction to an electrolytic process of water, that is, a reaction that the water is generated from hydrogen and oxygen.
Accordingly, each of the fuel battery cells is provided with a seal part for preventing a leakage of the fuel gas, the air, the water generated by the electrochemical reaction mentioned above, surplus air and the like. Further, as this kind of seal part, there has been known a seal part in which gaskets made of a rubber material or a synthetic resin material having a rubber-like elasticity are integrated with a separator or a film-shaped, sheet-shaped or plate-shaped base material such as a synthetic resin film or the like (refer, for example, to Japanese Patent No. 3820883).
FIG. 7 is a sectional view showing a seal part in which gaskets are integrally formed on both surfaces of a thin plate shaped base material, and FIG. 8 is a sectional view showing a conventional art for manufacturing the seal part in FIG. 7.
In this case, the seal part shown in FIG. 7 is provided with a thin plate shaped base material 1, and gaskets 2 which are integrally provided on both front and back faces thereof and are made of a rubber material or a synthetic resin material having a rubber-like elasticity, and these gaskets 2 have base portions 2a which are adhered to the base material 1, and seal lips 2b which protuberate in a ridge shape from upper surfaces thereof, and are brought into close contact with laminated separators (not shown) or the like with an appropriate collapsing margin, thereby achieving a sealing function with respect to the fuel gas or the air mentioned above.
In this seal part, the gaskets 2 are integrally formed on the base material 1 in accordance with a known molding method such as a liquid injection molding (LIM) or the like by using a liquid molding material. In detail, as shown in FIG. 8, a metal mold 100 constructed by split molds 101 to 103 is used, the base material 1 is positioned and fixed between the split molds 102 and 103, and the liquid molding material is filled into annular cavities 104 and 105 which are defined between the base material 1 and inner surfaces of the split molds 102 and 103 and communicate with each other via a communicating hole 1a provided in the base material 1, through a sprue 100a, a runner 100b and a gate 100c which are formed in the split molds 101 and 102, and hardened by cross linking.
In this case, since the gaskets 2 are made in an annular continuous shape (an endless shape), and the cavities 104 and 105 forming this have the same shape, the liquid molding material filled in the cavities 104 and 105 via the gate 100c and the communicating hole 1a is branched into both sides in peripheral directions to flow within the cavities 104 and 105 from the gate 100c and the communicating hole 1a, and so branched flows meet at an opposite side to the gate 100c and the communicating hole 1a. Further, since a molding defect caused due to remaining air, and vaporizing gas from the molding material tends to be caused in those confluent portions 104a and 105a, air vent grooves 104b and 105b for discharging out the remaining air and the vaporizing gas are formed along contact surfaces between the base material 1 and the split molds 102 and 103. Accordingly, a seal part manufactured in accordance with the method mentioned above is structured, as shown in FIG. 7, such that burrs 2c extending along a surface of the base material 1 from the base portions 2a of the gaskets 2 are formed by the molding material flowed into the air vent grooves 104b and 105b. 
However, in accordance with the forming method as mentioned above, for example, in the case that the seal lips 2b of the gasket 2 are brought into close contact with bottom surfaces of grooves formed in the separators, the burrs 2c formed by the air vent grooves 104b and 105b do not enter in the grooves, adversely affects a sealing performance of the gaskets 2, and cause a strain of the base material 1. Accordingly, it is necessary to remove the burrs 2c mentioned above after forming the gaskets 2. Particularly, since the burrs 2c exist on both surfaces of the base material 1 in the case that the gaskets 2 are provided on both surfaces of the base material 1, it takes an enormous time to carry out a removing work, and there is a risk that the base material 1 is broken at a time of removing the burrs.